The Japanese supercomputers originally grew out of the mainframe
families. The corresponding operating systems did the same, and since
the Japanese domestic operating systems were all inspired by IBM's
MVS, these mainframe systems also invaded the supercomputers. With
the latest series of high-end computers the Japanese manufacturers
have announced a serious stake in Unix. Fujitsu has had a version of
UTS (UTS/M), which it obtained from Amdahl in 1985, available on its
mainframes since 1986 (native since 1987). With the announcement of
the VP-2000 series Fujitsu has offered a consolidated Unix offering for
both environments, 'UXP/M', which is based on System V, release 4 and
being shipped since 1992. NEC also announced its version of Unix,
Super-UX, for its supercomputers, and started shipping in the first half
of 1991. Hitachi announced its new system, Hi-UX, with the
introduction of the S-3800 and S-3600 systems and they have now
started shipping. Japanese Cray systems are almost exclusively running
Unicos which is considered the most mature Unix-based supercomputer
operating system.